The proposed research involves a study of lens regeneration from the iris, neural retina regeneration from the pigmented, retinal epithelium and the reconstitution of a lens from lens epithelium in urodele amphibians. It is hoped to obtain information concerning the stimuli which release these metaplasias and the role of trophic factors during regeneration. Synthesis of macromolecules and cytological changes in the reacting tissues will also be studied. Some of the aspects to be investigated are the ultrastructural and synthetic events taking place in lens capsule formation during lens regeneration in adult newts and ultrastructural changes during dedifferentiation of the iris and beginning lens differentiation in young and old larvae. Surface changes in the dorsal iris, the formation of the lens capsule and the reconstitution of the zonule during lens regeneration will also be studied with the scanning electron microscope. DNA synthesis, cell proliferation and growth rates in embryonic lens vesicles developing in ocular and extra-ocular sites in larval hosts and possible similarities between the actions of the lens inductor from the embryonic eyecup and the neural retinal tropic factor during lens regeneration in organ culture will also be examined.